Bispectral analysis of mesosphere winds

Spectral components exist in the measured winds whose presence is not easily explained through known production mechanisms. Since the atmosphere is non-linear it is likely that non-linear interactions between tides and planetary waves will result in modulation of the tides with the associated production of new spectral components, possibly at the sum and/or difference frequency of the original components. This process has been suggested in the literature and spectral analysis of mesosphere winds has produced spectral components with this sum and difference relation. In an effort to show that these spectral components have properties that are consistent with this non-linear production process, meteor winds measured with the UNH Meteor radar at Durham (71 degrees W, 43 degrees N) were subjected to bispectral analysis. Results which involve interactions between tidal components only are expected and easily explained. However, other results are surprising and it is shown that some interactions that are known to occur do not show up in the analysis. (C) 1997 Elsevier Science Ltd.